Folic Acid Self-Assembly Enabling Manganese Single-Atom Electrocatalyst for Selective Nitrogen Reduction to Ammonia

Abstract

Efficient and robust single-atom catalysts (SACs) based on cheap and earth-abundant elements are highly desirable for electrochemical reduction of nitrogen to ammonia (NRR) under ambient conditions. Herein, for the first time, a Mn–N–C SAC consisting of isolated manganese atomic sites on ultrathin carbon nanosheets is developed via a template-free folic acid self-assembly strategy. The spontaneous molecular partial dissociation enables a facile fabrication process without being plagued by metal atom aggregation. Thanks to well-exposed atomic Mn active sites anchored on two-dimensional conductive carbon matrix, the catalyst exhibits excellent activity for NRR with high activity and selectivity, achieving a high Faradaic efficiency of 32.02% for ammonia synthesis at − 0.45 V versus reversible hydrogen electrode. Density functional theory calculations unveil the crucial role of atomic Mn sites in promoting N2 adsorption, activation and selective reduction to NH3 by the distal mechanism. This work provides a simple synthesis process for Mn–N–C SAC and a good platform for understanding the structure-activity relationship of atomic Mn sites. Graphic Abstract

High-loading metal atoms on graphdiyne for efficient nitrogen fixation to ammonia

“…These results outperform those of most atomic NRR electrocatalysts and even some nano-scale materials (Table S1 †). [38][39][40][41][42][43][44][45][46] Electrochemical reduction reactions were performed under an Ar atmosphere to conrm the nitrogen source of the detected ammonia. No ammonia could be detected when Ar was applied as the feeding gas (Fig.…”

Macro/Micro‐Environment Regulating Carbon‐Supported Single‐Atom Catalysts for Hydrogen/Oxygen Conversion Reactions

“…[41] Defective graphene with N, O dangling bonds can extract metal atoms species away from bulk Co or Fe foams and convert them to SACs subsequently via a thermal treatment process. [42] The direct pyrolysis of 2D supramolecular nanosheets [43] and 2D metal-organic-framework (MOF) [44][45][46] or molten salt-assisted pyrolysis strategy [47][48][49] have shown huge potential for the generation of 2D layered structured carbon-supported SACs. For example, the Cu SACs on 2D porous nanosheets were produced by pyrolysis of 2D dual metal Zn/Cu MOFs.…”

Research Progress and Perspectives on Active Sites of Photo- and Electrocatalytic Nitrogen Reduction

“…Therefore, it is still a great challenge to prepare highly dispersed Mn SACs. 199 By controlling the Mn−O bonding conditions, Han et al 198 realized the local modulation of single-atomic Mn and constructed a single Mn−O 3 N 1 anchored porous carbon (Mn−O 3 N 1 /PC) for NRR. With this strategy, more electrons were transferred to the adsorbed N 2 molecules via Mn−O 3 N 1 sites than via Mn−N 4 sites, as summarized in Figure 26f.…”

“…Taking into account the cost effects, earth-abundant non-noble metals (Fe, − Cu, Mo, , and Mn , ) greatly attracted much attention compared to the noble metals. Zhang et al prepared an Fe-SnO 2 catalyst for NRR by a simple hydrothermal reaction.…”

“…Mn single atoms are easily oxidized after heat treatment, and they will also aggregate into oxides/carbides even if the content is very low. Therefore, it is still a great challenge to prepare highly dispersed Mn SACs . By controlling the Mn–O bonding conditions, Han et al realized the local modulation of single-atomic Mn and constructed a single Mn–O 3 N 1 anchored porous carbon (Mn–O 3 N 1 /PC) for NRR.…”